During the processing of vegetable oils, such as soybean oil or corn oil, such oils are usually subjected to a high temperature steam distillation step under high vacuum to distill off volatile material which produces undesirable flavors and odors in the oil. This operation is usually referred to as deodorization. The materials causing such flavors and odors are largely unidentified, but the distillates from the deodorization ("deodorizer distillate") contains substantial quantities of fatty materials including free fatty acids, glycerides of fatty acids and unsaponifiables such as sterols and tocopherols. The sterol portion of the deodorizer distillate contains a mixture of sterols such as stigmasterol, sitosterol, and campesterol. Of the sterols, stigmasterol is particularly valuable as an intermediate for the preparation of certain pharmaceuticals such as sex hormones, cortisone, and the like.
Several processes for purification of sterols from deodorizer distillate or related materials are known in the art. For example, U.S. Pat. No. 2,704,764 discloses a general process for transesterification of deodorizer distillate, the esterification of fatty acids, and the isolation of sterols using an alcohol solvent. U.S. Pat. No. 2,729,655 discloses recovering sterols from deodorizer distillate by dissolving the methyl esters in a petroleum hydrocarbon solvent and saturating the resulting solution with water to precipitate the sterols. U.S. Pat. No. 2,843,610 discloses treating deodorizer distillate by saponification and esterification followed by crystallization of the sterols with acetone, methanol and water. Finally, U.S. Pat. No. 2,870,176 discloses recrystallization of a phytosterol concentrate from anhydrous heptane which provides an enrichment of the stigmasterol content.
It would be highly desirable to have a process which improves upon the prior art by providing a product with improved yield and purity of stigmasterol from deodorizer distillate.